1. Field of the Invention
The present invention relates to an IC socket for carrying out various tests of an IC package, in which a socket frame is attached to a test board via a contact sheet. Particularly, the present invention relates to an IC socket for mounting an IC package to a test board via a contact sheet for the purpose of carrying out the high frequency test.
2. Description of the Related Art
An IC socket has been known in the prior art, for carrying out various tests such as a high frequency test for an electronic part such as an IC package or others in which the IC package is mounted to an IC socket attached to a test board via a contact sheet and secured by a pusher such as a pressure plate.
The contact sheet in such a conventional IC socket and the steps for manufacturing the same are illustrated in FIGS. 14 to 24. First, FIG. 14 is a perspective view of the contact sheet of the prior art IC socket; FIG. 15 is a perspective view of a back surface of the contact sheet shown in FIG. 14; FIG. 16 is an enlarged sectional view of a mounting screw when the prior art IC socket is assembled; FIG. 17 is a sectional view of part of the prior art IC socket along the mounting screws when the socket frame is warped during the manufacture or the assembly thereof; FIG. 18 is a sectional view of part of the prior art IC socket along the mounting screws when the socket frame is inclined during the manufacture or assembly thereof; FIG. 19 is a perspective view illustrating the stamping of a sheet at a first step of the manufacture of the conventional IC socket; FIG. 20 is a perspective view illustrating the temporary application of adhesive at a second step subsequent to FIG. 19; FIG. 21 is a perspective view illustrating the etching of contacts at a third step subsequent to FIG. 20; FIG. 22 is a perspective view illustrating the press-bending of the contacts at a fourth step subsequent to FIG. 21; FIG. 23 is a perspective view illustrating the thermocompression bonding of the contacts and the sheet at a fifth step subsequent to FIG. 22; and FIG. 24 is a perspective view illustrating the cutting of excessive portions of the contacts at a sixth step subsequent to FIG. 23.
The prior art IC socket basically has the same structure as that of the present invention shown in FIGS. 1 and 2, wherein a contact sheet is placed on a test board, and a socket frame is mounted and fixed thereon by screws and nuts to form an integral body.
As shown in FIGS. 14 and 15, a contact sheet 103 used for the prior art IC socket has a plurality of contacts 108 of elastic metallic strips which are adhered to an insulation film 109, for example, of polyimide via a heat-compressive adhesive sheet 111. One end 108a of the respective elastic metallic strips of the contact 108 are positioned on circuits of a test board 102, and the insulation film 109 is adhered thereon so that free ends 108b of the contacts 108 are bent to have a wave shape.
For example, as shown in FIGS. 16 to 18, such a contact sheet 103 of the prior art IC socket is placed on the test board 102, and the socket frame 104 is mounted thereon, which assembly is then fastened together with screws 105 and nuts 106. Since it is adapted that the IC package (not shown) is mounted on the fastened socket frame 104 so that IC leads are disposed on the contacts 108 and pressed by a pusher (not shown), the free ends 108b of the contacts 108 are located above the circuits of the test board 102 to make the electric connection between the both.
In the prior art IC socket 100 of such a structure, when the contact sheet is mounted on the test board 102, a gap S is created between the test board 102 and the contact sheet 103 as shown in FIGS. 16 to 18. If the mounting screws 105 are threaded and fastened with nuts 106, the socket frame 104 may be warped or inclined, resulting in that a problem in that the socket frame 104 can not uniformly press the contact sheet 103.
The steps of the manufacture of the prior art contact sheet used for the IC socket described above are shown in FIGS. 19 to 24.
First, as shown in FIG. 19, at a first step of the manufacture of the contact sheet for the IC socket, an insulation film 109 such as that of polyimide is stamped to have the illustrated shape. On the respective opposite edge of the stamped insulation film 109 of the illustrated shape, the heat-compressive adhesive sheet 111 used as an adhesive is temporarily adhered at a second step as shown in FIG. 20. Simultaneously therewith, or subsequently thereto, the contacts 108 are formed by an etching from a suitable sheet metal 107 at a third step as shown in FIG. 21, whereby metallic strips as a raw material of the contacts 108 are prepared.
Then, at a fourth step as shown in FIG. 22, the contacts are bent by a press machine to form bending free ends 108b of the contacts 108. Thereafter, the insulation film 109 on which the heat-compressive adhesive sheet 111 is temporarily adhered is placed on the sheet metal 107 having free ends 108b of the contacts 108 as a fifth step shown in FIG. 23.
Excessive portions on the periphery of the sheet metal 107 of the contact sheet 103 on which the insulation film 109 is heat-compressively adhered is cut off as a sixth step, and the contact sheet 103 of a required shape is formed as shown in FIG. 24.
However, in the prior art IC socket 100 using such a contact sheet 103, when it is mounted onto the test board 102 as described above, the gap S may be created between the test board 102 and the contact sheet 103. If the mounting screws 105 are fastened under the condition, the socket frame 104 may be warped or inclined, resulting in the problem in that the socket frame 104 can not uniformly press the contact sheet 103.
Accordingly, an object of the present invention is to provide an IC socket having a spacer member in a contact sheet so that the contact sheet is in tight contact with a test board via the spacer member without any inclination when the socket frame is mounted to the test board via the contact sheet.